Equinus is a condition in which the upward bending motion of the ankle joint is limited. Someone with equinus lacks the flexibility to bring the top of the foot toward the front of the leg. Equinus can occur in one or both feet. When it involves both feet, the limitation of motion is sometimes worse in one foot than in the other.
People with equinus develop ways to compensate for their limited ankle motion, and this often leads to other foot, leg or back problems. The most common methods of compensation are flattening of the arch or picking up the heel early when walking, placing increased pressure on the ball of the foot. Other patients compensate by toe walking, while a smaller number take steps by bending abnormally at the hip or knee.
Causes
There are several possible causes for the limited range of ankle motion. Often, it is due to tightness in the Achilles tendon or calf muscles (the soleus muscle and/or gastrocnemius muscle). In some patients, this tightness is congenital (present at birth), and sometimes it is an inherited trait. Other patients acquire the tightness from being in a cast, being on crutches or frequently wearing high-heeled shoes. In addition, diabetes can affect the fibers of the Achilles tendon and cause tightness. Sometimes equinus is related to a bone blocking the ankle motion. For example, a fragment of a broken bone following an ankle injury, or bone block, can get in the way and restrict motion. Equinus may also result from one leg being shorter than the other. Less often, equinus is caused by spasms in the calf muscle. These spasms may be signs of an underlying neurologic disorder.
Foot Problems Related to Equinus
Depending on how a patient compensates for the inability to bend properly at the ankle, a variety of foot conditions can develop, including:
- Plantar fasciitis (arch/heel pain)
- Calf cramping
- Tendonitis (inflammation in the Achilles tendon)
- Metatarsalgia (pain and/or callusing on the ball of the foot)
- Flatfoot
- Arthritis of the midfoot (middle area of the foot)
- Pressure sores on the ball of the foot or the arch
- Bunions and hammertoes
- Ankle pain
- Shin splints
When Is Surgery Needed?
In some cases, surgery may be needed to correct the cause of equinus if it is related to a tight tendon or a bone blocking the ankle motion. The foot and ankle surgeon will determine the type of procedure that is best suited to the individual patient.